JPH09291378A - Coated cemented carbide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve wear resistance and chipping resistance under various machining conditions by regulating the amounts of zirconium and hafnium, contained in a base material made of tungsten-carbide-base cemented carbide, and also regulating the distribution of binding phases in the base material. SOLUTION: A base material is made of WC-base cemented carbide containing Zr and Hf. At this time, 0.01<=M1 /M2 <0.25, by mole ratio, is satisfied when M1 and M2 represent the total content of Zr and Hf and the total content of Ti, respectively, and further, a layer enriched in binding phase, having a binding phase concentration higher than the average binding phase concentration in the base material, is provided onto the part in the vicinity of the surface of the base material. Subsequently, a TiN layer, as inner layer to be in contact with the base material, and a TiCN layer, as intermediate layer to be in contact with the inner layer, are provided. Further, an outer layer, which is composed of one or more substances selected from TiC, TiCN, Ti carbonate, Ti carbonitrooxide, and Al2 O3 and consists of one or more layers including at least one or more Al2 O3 layers, is formed on the intermediate layer. Moreover, although the thickness of the intermediate layer is regulated so that it is larger than that of the outer layer, the total thickness of these three layers is regulated to 8-30μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated cemented carbide having excellent wear resistance suitable for a cutting tool and the like, and more particularly to a coated cemented carbide suitable for a cutting tool suitable for cutting steel.

[0002]

2. Description of the Related Art Conventionally, as described in, for example, JP-A-8-1408 and JP-A-8-71814, Al ₂ is further formed on a cemented carbide substrate through a film of TiC, TiN, TiCN or the like. It is used as a cutting tool with excellent wear resistance by depositing an O ₃ film. In addition, JP-A-6-330
Japanese Patent No. 352 improves the fracture resistance of a tool by shot peening with a high projection speed.

[0003]

In recent years, along with the demand for labor saving and unmanned cutting, there is a tendency for tools with higher versatility and longer life to be required. An object of the present invention is to provide a tool material satisfying a wide range of wear resistance and fracture resistance that can be used under various cutting conditions in order to meet this demand. In addition, we provide tools with improved fracture resistance by shot peening at a lower cost, and also solve the problem of deposit separation damage due to the recent increase in cutting speed and obtain a smooth work surface. I will provide a.

[0004]

[Means and Actions for Solving the Problems] In order to solve the above problems, various studies have been conducted focusing on the conventional coated cemented carbide, and as a result, the present invention has been accomplished based on the findings.
The obtained knowledge and the constitution of the present invention will be described below.

First, the base cemented carbide is a WC-based cemented carbide containing Zr and / or Hf. Zr and Hf improve the plastic deformation resistance of the substrate, especially at a high temperature such as the cutting edge temperature during cutting, and eventually improve the wear resistance.
Most of these elements exist in the alloy in the form of a solid solution with a carbide of titanium or the like, so that the optimum Zr,
The amount of Hf is a molar ratio with Ti: 0.01 ≦ M ₁ / M ₂ <
It is expressed as 0.25. However, M ₁ is the total amount of Zr and Hf, and M ₂ is the total amount of Ti. If this value is less than 0.01, it is difficult to obtain a sufficient effect, and conversely, if it is 0.25 or more, the fracture resistance deteriorates. Even if the above formula is satisfied, addition of 0.3 wt% or more with respect to the entire base alloy causes embrittlement of the alloy, which is not preferable.

Second, the cemented carbide substrate is provided with a binder phase enriched layer near the surface prior to coating. Here, the binder phase-enriched layer is a layer having a binder phase concentration relatively enriched with respect to the average binder phase concentration of the substrate, and from the viewpoint of hardness, it is also referred to as a hardness-reduced layer or a soft layer. being called. Further, when there is a region in which the β phase disappears in this layer, the region may be referred to as a β-free layer. By providing this, the toughness of the substrate is increased, and chipping resistance and chipping resistance are improved. However, the hardness of this portion is lower than that of the inside of the substrate, and there is concern that the cutting edge may be plastically deformed. However, if the thickness of the binder phase enriched layer is about 10 to 30 μm, deterioration of the plastic deformation resistance of the cutting edge during cutting is not a problem.

Further, the binder phase enriched layer also works effectively in adjusting the residual stress in the coating layer, as described later.

The binder phase-enriched layer can be provided by various methods. Specifically, nitrogen is incorporated into the cemented carbide substrate component by adding, for example, TiN. And is generated in the sintering process. this is,
Due to denitrification from the surface of the substrate during the sintering process, Ti and the like near the surface melt into the liquid phase and migrate solute inside the substrate,
It is considered that the bonding layer in the vicinity of the surface of the substrate is relatively enriched because it is precipitated as a carbide within the substrate.
The thickness of the binder phase enriched layer and the degree of enrichment can be easily controlled by adjusting the amount of nitrogen added and the heat treatment time. The degree of binder phase enrichment can be determined by, for example, EPMA (Electr)
on probe microanalysis) and the like, it can be clearly grasped by line analysis.

If the cutting edge is subjected to a honing treatment or the like after the binder phase-enriched layer is provided, the binder phase-enriched layer in that portion may be removed. In order to prevent this, there are a method of providing a binder phase-enriched layer after processing, a method of powder compacting, or a method of adjusting the shape of the cutting edge of the powder compact. However, the cutting edge is basically a part that slides on the work material during cutting, and a strong impact force is not applied, so rather from the viewpoint of wear resistance it may be convenient not to have a binder phase enriched layer. Many.

Thirdly, it is preferable that the amount of binder phase is small on the surface of the substrate. This is to prevent the diffusion of the binder phase component into the film to be deposited later and prevent the deterioration of the film quality,
It is also for improving the adhesion between the coating layer and the substrate. Usually, in the surface of a cemented carbide substrate having a sintered surface, the binder phase metal oozes out from the inside of the substrate during the sintering process, and is in a state rich in the binder phase. In order to reduce the binder phase on the surface of the substrate, for example, a chemical acid treatment may be performed after sintering the substrate, but a method of heat treatment is convenient. Specifically, after vacuum sintering of the substrate, if an atmospheric gas of about atmospheric pressure is introduced into the furnace during cooling to cool the substrate, exudation of the binder phase is suppressed, and a surface with a reduced binder phase is obtained. The degree of reduction of the bonded phase on the surface is determined by, for example, EDX (Energy).
Dispersive X-ray spectro
It can be confirmed by performing surface analysis such as (metr) on the outermost surface of the substrate and the cross section of the substrate.

Fourth, a TiN layer is provided as an inner layer in contact with the substrate. This prevents the diffusion of carbon from the substrate during vapor deposition and prevents the generation of a brittle η phase on the substrate.
Further, Co is prevented from diffusing from the substrate and deterioration of the film quality is prevented. It is sufficient that the thickness of this layer is about 0.2 to 1 μm. If it is excessively thick, not only the film formation time will be lost, but also the production efficiency will be impaired, and the thickness of the entire coating layer will be increased, which will be described later. Adversely affects the peel resistance of.

Fifth, TiC is used as an intermediate layer in contact with the inner layer.
An N layer is provided. This layer exhibits outstanding wear resistance in cutting steel. This layer has a reaction gas composition of, for example, TiC.
_{l 4: 1~10%, CH 3} CN: 0.1~5%, N 2: 0
˜35, H ₂ : the rest (both of which are vol%), the reaction temperature is preferably 700 to 950 ° C., and the furnace pressure is preferably 30 to 200 torr. At this time, Cl resulting from TiCl ₄ remains in the coating layer, but the residual amount is preferably more than 0.05 at% and 1.2 at% or less. Within this range, the intermediate layer becomes fine columnar crystals and exhibits better wear resistance. If it is less than 0.05 at%, the crystal becomes coarse and becomes a fragile layer, and if it is more than 1.2 at%, the hardness is lowered and the adhesion of the coating layer is also lowered, which leads to a shortened tool life. . The amount of Cl can be confirmed by EPMA. The amount of Cl is adjusted by appropriately adjusting the vapor deposition temperature, the composition of the reaction gas, the vapor deposition time and the like. Since this layer is provided for the purpose of abrasion resistance, it is basically better to be thick, but there is a limit to the total thickness of the coating layer, so that the thickness is actually limited. The intermediate layer preferably has a thickness of 8 μm or more, more preferably 9.5 μm or more.

Sixth, the outer layer in contact with the intermediate layer is made of at least one substance selected from titanium carbide, titanium nitride, titanium carbonitride, titanium carbonate, titanium oxycarbonitride, and alumina. At least one layer including an alumina layer is provided. The alumina layer has excellent heat resistance and oxidation resistance, and mainly serves to prevent oxidation of the intermediate layer and the inner layer due to the temperature rise of the cutting edge during cutting. When the alumina layer is not provided, for example, FCD7 with a throw-away tool
In turning processing such as 0, boundary wear of the cutting edge progresses extremely quickly. If the thickness of the alumina layer is 1 μm or more, the above-mentioned purpose is achieved. On the other hand, if the thickness is too thick, the alumina layer will be easily peeled off, so that the thickness is preferably less than 2.5 μm. Particularly, when the thickness of the alumina layer is 4 μm or more, peeling is very likely to occur. A more preferable range is 1.3 μm or more and 1.7 μm or less. Further, the alumina layer has an effect of preventing welding if it is on the outermost surface of the cutting edge during cutting due to its poor wettability. The titanium compound layer provided in the outer layer so as to be in contact with the interface of the alumina layer on the substrate side mainly plays a role of enhancing the adhesive force of the alumina layer. In particular, TiC
900 to 11 using L ₄ , CH ₄ , N ₂ , CO ₂ , H _2, etc.
When chemical vapor deposition is performed at a relatively high temperature of about 00 ° C., it becomes granular crystal grains and exhibits strong adhesion. The thickness of this layer is 1
Less than μm is sufficient.

On the other hand, a colored layer is often provided as the outermost layer of the coating layer. For example, if a TiN layer is provided, the chip will have a beautiful golden color. This layer is provided for the purpose of making it easier to distinguish whether the tool is used or not. Therefore, unlike other layers, it is preferable that this layer is rather easy to peel off, and it is preferable that it is thin enough not to impair visibility. On the other hand, if this layer is difficult to peel off or wear away, the result is that the adhesion resistance of alumina is not utilized at all, which causes damage to the separation of the deposit and causes roughening of the work. To provide the outermost layer that is easily peeled off, for example, a large number of holes may be provided between adjacent layers. Specifically, treatment such as shot blasting described below may be performed before coating the outermost layer, and the outermost layer may be provided without precision cleaning.

Seventh, the total thickness of the coating layer thus provided is closely related to the peeling resistance of the coating layer. As a result of repeated experiments and examinations, the optimum thickness was 8 μm or more and 30 μm or less when a steel cutting tool was supposed to be used. However, the thickness of the outermost layer provided intentionally so as to be easily peeled off is not included. When the thickness is less than 8 μm, the thickness of each layer as described above cannot sufficiently be exhibited. If it exceeds 30 μm, the coating layer is likely to peel off, which is particularly disadvantageous for intermittent cutting. If you mainly think about cutting steel, make the wear-resistant intermediate layer as thick as possible,
If the other layers are thin enough to perform their respective functions, a tool with a longer life can be obtained. If the cutting temperature of the cast iron or the like, where the temperature of the cutting edge tends to rise relatively, is the main purpose, the alumina may be provided thick by taking advantage of the heat resistance of the above-mentioned alumina.

Eighth, it is known that the surface of the coated cemented carbide is treated by mechanical impact, thermal impact, ultrasonic impact or the like in order to further enhance the peeling resistance and fracture resistance of the coating layer. ing. This is intended to release the residual tensile stress generated in the coating layer in the process of forming the coating layer, or to give the residual stress even to the region of compressive stress. As a concrete method, processing by shot peening or shot blasting is well known, and shot projection speed is increased in order to make the processing by shot peening more effective. . However, in order to increase the shot projection speed, a higher performance device is required, which is costly.

In the present invention, this problem is solved by adopting the above-mentioned binder phase enriched layer as the substrate. The inventors of the present application have found that the higher the hardness of the substrate, the smaller the effect of releasing stress in the coating layer by the shot treatment. On the basis of this finding, when a binder phase-enriched layer having a low hardness was provided immediately below the coating layer, the conventional low projection speed (projection speed = 40 to 5) was obtained.
It was found that a sufficient effect can be obtained with a shot device of 0 m / s). Although the reason for this is not yet fully clear, it is probably the portion of the coating layer where the largest residual stress is applied due to the large deformation of the coating layer upon impact due to the soft substrate surface. In the part that touches the base,
This is because tensile stress due to deformation due to impact is concentrated, and cracks can be efficiently generated in the coating layer.
So I thought.

The value of the residual stress is 2θ-si by X-ray diffraction.
It can be measured by the n ² Ψ method. The specific residual stress value may be adjusted to ± 10 kgf / mm ² (± 98 MPa). Here, the symbol "+" indicates tensile stress, and the symbol "-" indicates compressive stress. Residual tensile stress in coating layer 20-30kg
When a glass ball having a particle diameter of 0.5 mm was shot at a projection speed of 40 m / s with respect to a coated cemented carbide of f / mm ² , the residual stress was 0 to ² kg / mm ^{2 in} 5 minutes, and it was almost completely released. Further processing continues for a total of 10 minutes, -6 to 0
It became kg / mm ² . Further treatment was continued to reach -11 kg / mm ² for a total of 20 minutes. After that, the treatment was added and the treatment was performed for a total of 120 minutes, but the increase in residual compressive stress was small and was -12 kg / mm ² . Those with a residual stress in the compression region are particularly excellent in fracture resistance, but require a long processing time, and also increase the damage rate of the product due to shot processing and reduce the product yield. Practically ± 10 kgf / mm
² is appropriate. If the residual tensile stress is 10 kgf / mm ² or more, chipping resistance and chipping resistance are poor. In addition to glass balls, ceramic balls, steel grids, alumina, cemented carbide and the like can be used as the shot material.

[0019]

EXAMPLES Next, examples will be specifically described. WC, Co, TiC, TiCN, TaC, Zr as raw material powder
C and HfC were prepared, and predetermined amounts were mixed so that the composition of the substrate was as shown in Table 1, and then wet-mixed with a ball mill,
CNM through each process of drying, powder compaction, sintering and grinding
A cutting tip of G120408 type was obtained. Then, TiN is 0.3 μm as the inner layer and TiCN is 1 as the intermediate layer.
0 μm, TiC 0.5 μm as an outer layer, Al ₂ O ₃ 1.5 μm, and TiN 0.5 μm were provided by a chemical vapor deposition method. The amount of Cl in the intermediate layer was 0.5 at%. Further, the residual stress in the coating layers of the samples other than the sample No. 5 was adjusted to be within ± 5 kgf / mm ² by shot peening. However, with respect to Sample No. 5, a residual tensile stress of 13 kgf / mm ² remained after shot peening. These were subjected to cutting tests by the following three types of turning.

As Test 1, the work material: S53C round bar,
Cutting speed: 250 m / min, feed: 0.4 mm / re
v, Depth of cut: 2 mm, the wear width of the negative surface of the chip after cutting for 20 minutes by a wet method was measured. As test 2, work material: FCD70 round bar, cutting speed: 150 m / m
In, feed: 0.3 mm / rev, depth of cut: 2 mm, and the wear width of the negative surface of the chip after cutting for 20 minutes by a wet method was measured. Test 3 to check tool fracture resistance
Was done. As Test 3, Work Material: SCM435 4
Round bar with groove, cutting speed: 150 m / min, feed: 0.
3 mm / rev, depth of cut: 2 mm, wet cutting was performed for 30 seconds. This was repeated 10 times to check the number of defects and chippings. The above results are collectively shown in Table 1.

[0021]

[Table 1]

Those containing neither Zr nor Hf wear quickly because the cutting edge is plastically deformed during cutting, and the test 1,
It became impossible to cut during Test 2. Those containing too much Zr were brittle and many defects were generated in Test 3. Those without the binder phase enriched layer produced chipping in tests 1 and 2. In the case of γ ₁ / γ ₂ ≧ 1, there was no problem in Test 1, but in other cases, the film tended to peel off slightly.
The performance with Hf added was almost the same as that with Zr added.

The above cutting test was conducted in the same manner as in Sample No. 3 except that the constitution of the coating layer was changed. Table 2 summarizes the results.

[0024]

[Table 2]

When the TiCN layer and the Al ₂ O ₃ layer were too thick, abrasion was considered to be caused by the falling of the coating layer. Those without adjusting the residual stress tended to cause chipping and chipping. Boundary wear was conspicuous for the thin Al ₂ O ₃ . A TiCN layer with a large amount of Cl has a fast wear, and a small amount has a poor fracture resistance. With respect to sample No. 17, the degree of chip wear was equivalent to that of sample No. 3, but the surface roughness of the work material at the early stage of cutting was good. The surface roughness of the surface to be cut was R _max = 50 to 60 μm in the case of cutting for 1 minute under the condition of Test 1 of Sample No. 3, but in the case of Sample No. 17, R _max was 37 μm.

[0026]

EFFECTS OF THE INVENTION The product of the present invention can withstand long-term use under a wider range of cutting conditions than that of the conventional product and can obtain a good work surface. Therefore, it exhibits excellent performance as a highly versatile cutting tool material suitable for labor saving and unmanned cutting.

Claims (16)

[Claims] 1. A molar ratio of 0.01 ≦ M ₁ / when the total amount of zirconium and hafnium of the tungsten carbide based cemented carbide substrate containing zirconium and / or hafnium is M ₁ and the total amount of titanium is M _2. M ₂ <0.25,
A binder phase-enriched layer having a binder phase richer than the average binder phase content of the substrate is provided near the surface of the substrate, and a titanium nitride layer is provided as an inner layer in contact with the substrate. A layer made of titanium carbonitride is provided as a contacting intermediate layer, and an outer layer in contact with the intermediate layer is made of one or more substances selected from titanium carbide, titanium nitride, titanium carbonitride, titanium carbonate, titanium carbonitride oxide, and alumina. And a coated cemented carbide, wherein at least one layer including at least one alumina layer is provided. 2. The binder phase content on the surface of the substrate is γ
_1. The coated cemented carbide according to claim 1, wherein a cemented carbide substrate having γ ₁ / γ ₂ ≦ 1 when the average binder phase content inside the substrate is γ _2. . 3. The coated cemented carbide according to claim 1, wherein the intermediate layer comprises columnar crystals. 4. The coated cemented carbide according to claim 3, wherein the thickness of the intermediate layer is larger than the thickness of the outer layer. 5. The coated cemented carbide according to claim 1, wherein the intermediate layer is a titanium carbonitride layer containing Cl in an amount of more than 0.01 at% and 1.2 at% or less. . 6. The coated cemented carbide according to claim 1, wherein the total thickness of all layers of the inner layer, the intermediate layer, and the outer layer is 8 μm or more and 30 μm or less. 7. A thickness of at least 1 μm and 2.5 μm
Coated cemented carbide according to claims 1 to 6, characterized in that the outer layer comprises less than a layer of alumina. 8. The coated cemented carbide according to claim 7, wherein the thickness of the alumina layer is 1.3 μm or more and 1.7 μm or less. 9. The method according to claim 1, wherein the outer layer includes at least an alumina layer and a titanium compound layer in contact with the alumina layer on the substrate side, and the thickness of the titanium compound layer is less than 1 μm. The coated cemented carbide described. 10. The coated cemented carbide according to claim 9, wherein the titanium compound layer is a titanium carbide layer. 11. The coated cemented carbide according to claim 1, wherein the intermediate layer has a thickness of 8 μm or more. 12. The coated cemented carbide according to claim 11, wherein the thickness of the intermediate layer is 9.5 μm or more. 13. The outermost layer, which is the outermost layer of the outer layers, contains at least titanium and nitrogen.
13. The coated cemented carbide according to any one of 1 to 12 above, wherein voids are present between the outermost layer and a layer in contact with the outermost layer. 14. A molar ratio of 0.01 ≦ M ₁ / when the total amount of zirconium and hafnium in the tungsten carbide based cemented carbide substrate containing zirconium and / or hafnium is M ₁ and the total amount of titanium is M _2. M ₂ <0.25, having a binder phase-enriched layer in which the binder phase is richer than the average binder phase content of the substrate near the surface of the substrate, and titanium nitride is used as an inner layer in contact with the substrate. And a layer made of titanium carbonitride as an intermediate layer in contact with the inner layer, and titanium carbide, titanium nitride, titanium carbonitride, titanium carbonate, titanium carbonitride oxide, alumina as an outer layer in contact with the intermediate layer. A coated cemented carbide comprising one or more substances selected from the group consisting of at least one alumina layer and at least one layer, and then the coated cemented carbide surface is formed by mechanical impact on the coated cemented carbide surface. Processed Coated cemented carbide characterized and. 15. The outermost layer, which is the outermost layer of the outer layers, contains at least titanium and nitrogen, and is treated by mechanical impact before the outermost layer is provided. The coated cemented carbide according to. 16. The residual stress in the coating layer is -0.1 to +.
It is 0.1 GPa, It is characterized by the above-mentioned.
5. The coated cemented carbide according to item 5.